Since cutting inserts for rough machining large workpieces are placed under heavy loads, they are relatively large in size and are provided with a broad supporting surface on the bottom. Generally, since roughing inserts of this kind have a relatively large depth of cut and feed rate, they are fixed to the pocket of a tool holder by a lever projected through a pocket base, and not by a clamp coupled from above, to minimize interference.
However, since conventional roughing inserts are provided with cutting edges only on the upper surface, they are discarded when the cutting edges on the upper surface are worn out, which is uneconomical.